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Questions tagged [fourier-descriptors]

Fourier descriptors are a way of encoding the shape of a two-dimensional object by taking the Fourier transform of the boundary, where every point on the boundary is mapped to a complex number.

Fourier descriptors are a way of encoding the shape of a two-dimensional object by taking the Fourier transform of the boundary, where every point on the boundary is mapped to a complex number. The original shape can be recovered from the inverse Fourier transform. However, if only a few terms of the inverse are used, the boundary becomes simplified, providing a way to smooth or filter the boundary.

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Extracting Fourier Descriptors from Images with Python

I have some images of tags with shapes on them (circle, rectangle and blank). After processing the images with median blur and Gabor filters I can eliminate most of the effect that variable illumination had on the images and they look like…
Jack Simpson
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Matlab fourier descriptors what's wrong?

I am using Gonzalez frdescp function to get Fourier descriptors of a boundary. I use this code, and I get two totally different sets of numbers describing two identical but different in scale shapes. So what is wrong? im =…
Adham shafik
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I want to reduce the time to compute 2D FFT in C++ on 100 million complex data

I am trying to compute 2D FFT on 100 million complex data (100000x1000) and it is taking 4.6 seconds approximately, but I want to reduce time. Then I tried to compute it using fftw_thread. But then the computation time has increased (in 2 threads…
Siddhartha Roy
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Interpreting Prophet Output for Weekly and Yearly Seasonality

I am going through the tutorial for using prophet in R. You can find the dataset here: https://github.com/facebookincubator/prophet/blob/master/examples/example_wp_peyton_manning.csv # R library(prophet) library(dplyr) df <-…
nak5120
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Discrete Fourier Transform implementation gives different result than OpenCV DFT

We have implemented DFT and wanted to test it with OpenCV's implementation. The results are different. our DFT's results are in order from smallest to biggest, whereas OpenCV's results are not in any order. the first (0th) value is the same for…
Silex
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Matlab: 2D Discrete Fourier Transform and Inverse

I'm trying to run a program in matlab to obtain the direct and inverse DFT for a grey scale image, but I'm not able to recover the original image after applying the inverse. I'm getting complex numbers as my inverse output. Is like i'm losing…
Daniel Arevalo
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How to load a sequence of elliptic Fourier coefficients into R to make an outline analysis in Momocs package?

I'm novice with R. I have a text file with precalculated sequence of elliptic Fourier coefficients (harmonics). The first column keeps the objects name, other - sets of harmonics divides by spaces: A0 B0 C0 D0 ... An Bn Cn Dn. It is the part of a…
Ivan Z
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How to normalize elliptic fourier coefficients?

I'm writing a program to find an Elliptic Fourier Coefficients (EFC) of a closed planar curve, and have a trouble with coefficients normalization. The closed planar polyline p is described by the set of points m_points: m_points[i][0] keeps…
Ivan Z
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Computing Fourier Series to represent data points

I wish to compute a function (a Fourier series) that passes through some set of given points. Similar to what is going on here https://gofigure.impara.ai/ , but I wish not to animate it. I merely want the function so that I can draw the shape…
Francesco
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Fourier descriptors in MATLAB

I'm trying to find the matching score between the boundary of shapes that do not exactly match. I use Fourier descriptor to represent these boundaries and find the similarity based on DTW as follows: (X,Y) is the coordinate points of the boundary…
drq40
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Fourier Shape Descriptors

I'm looking at a paper named "Shape Based Image Retrieval Using Generic Fourier Descriptors", but only have rudimentary knowledge of Fourier Descriptors. I am attempting to implement the algorithm on page 12 of the paper, and have some results…
Paul
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What are the prerequisite to understand Fourier Descriptor program in matlab?

I am new to Digital Image Processing and have to simulate a Fourier Descriptor Program that is Affine Invariant, I want to know the prerequisites required to be able to understand this program, my reference is Digital Image Processing Using MATLAB…
Userhanu
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how to make a program for calculating a fourier series

I'm a guy just playing with Fourier series. I created a python program for it, but I don't know how to calculate the arms so that it finally draws specific shapes or images. Here is my program: https://github.com/KikiZC/Projekt-Tocky. thank you for…
Kiki ZC
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Getting Fourier Descriptors from (x,y) points in Python for Reconstruction

I have seen a lot of videos online which talk about getting Fourier descriptors from (x,y) points by using a Discrete Fourier Transform, and then using some of these Fourier descriptors to reconstruct the approximate boundary. This approximation…
PyTorchLearner
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How to assign manually colors to each data group

Could someone help me in assigning a manual colour to each group? I want to use these two colours for my data #F96167 for beer, and #FCE77D for Whisky. Also, in the last graph, I would like different plot symbols (e.g. ∆ for Beer, O for Whisky) for…
Umar KHAN
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